Control and supervising apparatus for oil burners



Jan. 22, 1963 R. LUD] 3,074,471

CONTROL AND SUPERVISING APPARATUS FOR on. BURNERS Filed Jan. 10, 1961 2 Sheets-Sheet 1 Fig. 7

I N VEN TOR.

Roger AL dd GLLANJ ATTQ 555 Jan. 22, 1963 R. LUDI 3,074,471 CONTROL AND SUPERVISING APPARATUS FOR OIL BURNERS Filed Jan. 10, 1961 2 Sheets-Sheet 2 I /5 Fig. 4 3 6 I Y Q 76 l7 [0 A II D El Big 22 15 74 I i I a 25 m1 Y 1 8 '1 I A? 1n I 1 0 I 111' 0r 1 24 L: 27 1"1 INVENTOR. 20 e, .Ad/dd TTO KNEiiS United States Patent Ofifice 3,024,471 Patented Jan. 22, 1953 3,'l}74,471 CGNTRGL AND SEJ'PERVESL'IIG APRHERATUS FGR 011. EU EP-iS The present invention relates to a control and supervising apparatus for oil burners.

The greatly increasing use of oil-fired furnace installations results mainly from the application of such control and supervising apparatus which effectively facilitate the start and operation of oil burners.

The basic function of such apparatus is to receive and discriminate various input signals and to process these data into appropriate output signals to ensure fail-safe start and operation of the oil burner. The nature of these signals, determined by the construction of the burner and the operating conditions of the plant, will become apparent from the following discussion of the schematic diagram FIG. 1. The control and supervising apparatus is represented herein by the rectangle X, the incoming signals by left arrows t, p, g and the outgoing signals by right arrows z, m,

A first input signal t calls for starting or shutting down the plant. It is produced in general by a thermostat, sometimes programmed by means of a time switch or controlled by a manually operated switch.

A second input signal p indicates whether a flame is established in the burner or not. This signal is obtainable from any photoelectric transducer exposed to the flame (flame detector), a photo-voltaic cell or a photo-couductive resistor being particularly appropriate in this case.

As a third input signal is considered the fault resetting action, represented by arrow g. This action consists of deliberately re-establishing the normal operating conditions after the apparatus X having reached for any reason the fault position. Usually a press button or key is provided for this purpose, with the possibility of remote operation if needed.

Responding to the above input signals 2, p and g in a definite manner, the apparatus X produces the output signals required for governing the oil burner, plant, including the ignition of the flame (Z), the control of the burner motor (m) and, occasionally, the indication of a fault (7).

For reasons specified hereinafter in greater detail, a characteristic time sequence is established between the output signals 2 and m: Initially, on starting the oil burner, only the ignition is to be switched on during a certain time, the so-called pre-ignition period. Following this period both the ignition and the motor are energized, this period being called the bridging or flame inception time. At the end of this period the ignition is switched olf and only the motor continues running, this state being the normal operating condition. Some of the control and supervising apparatus known in prior art may be technically satisfactory in operation, but all of them are more or less designed with a view to manufacture in small series. They consist substantially of a combination of per se known components Wired together in a suitable fashion. This kind of layout is not suitable, however, for manufacture in large series, and has a. particularly disadvantageous effect on the manufacturing price.

Accordingly an important object of the present invention is the provision of a control and supervising apparatus consisting of components specially designed for this specific field of use, and of a type which can be r economically manufactured and assembled in large quantities.

Another object of the present invention is to provide a reliable governing apparatus for automatic yet fail-safe start and operation of the oil burner plant.

A further object of the present invention is the provision of a control and supervising apparatus which is fully self-checking in operation in view of component failure.

Still another object of the present invention is, in a control and supervising apparatus for oil burners, the provision of a single time delay element for both the pre-ignition period and the flame inception period.

These and still further objects and the entire scope of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

FIG. 1 is a schematic diagram, referred to above,

FIG. 2 shows the arrangement of the chief mechanical components,

FIG. 3 is a section along lines Y-Y in FIG. 2, and

FIG. 4 is a complete connection diagram of the control and supervising apparatus.

In FIGURES 2, 3 and 4, like parts are designated with like references. The mechanical components shown in FIGS. 2 and 3 are mounted on a base plate 1, preferably together with the amplifier for the flame detecting device (not shown in FIG. 2). The means for measuring the pro-ignition and the bridging period when the burner is being put into operation is a bimetallic device C which is fixed to the base plate 1 by means of the mounting angle 2. Of two identical, parallel bimetallic strips 3 and 5 rivetted together with interposition of the spacer element 4, the first strip 3 serves for compensating for bending of strip 5 as a result of fluctuations in the ambient temperature. The second strip 5 carries an electrical heating coil 6 and bends in the direction indicated by the arrow when heated.

Arranged on the base plate 1 at both sides of the bimetallic device C are two change-over switches A and B which are constructed as snap switch. They are each composed of a stationary, bifurcated bearing element 9 and 15 respectively, a switching element 12 and 18 respectively, the associated stationary contacts 10, 11 and 16, 17 respectively, and a coil spring 13 and 19 respectively. With one end the coil springs 13 and 19 are fixed to the respective switching element 12 and 18, and with its other end the coil springs are anchored on a slide 8 which under the tension of these springs bears against the bearing elements 9 and 15 through the agency of the rockable levers 14 and 20, which are supported by a kind of knife-edge bearing arrangement. The shape and position of elements 8, 15, 18, 20 of switch B is shown more clearly in FIG. 3, which in its upper part is a section through the resting point of switching element 18 and in its lower part is a section through the resting point of lever 20; the switching element 18 is omitted partially for clarity. A transmission element 7 fixed on the heatable bimetallic strip 5 is engaged in the slide 8 and, when the end of the bimetallic strip is displaced upon heating, imparts to the said slide a shifting movement in the longitudinal direction thereof. This slide movement is transmitted to the levers 14 and 2t and also to the ends of the springs 13 and 19 which are anchored on the slide. As soon as, with the progressive displacement of slide 8 in the direction indicated by the arrow, the line of action of a spring 13 or 19, which is moving as well as the slide,

3 passes the bearing point of the relevant switching element 12 or 18, the latter suddenly switches-over and thereby brings the relevant switch into the operating position.

It is to be emphazised that the switching interval of switch B is greater than that of switch A, and exceeds the latter in both directions of movement of the slide 8.

vThe characteristic points in this respect are shown in FIG. 2 with reference to the various positions of the levers 14 and 20 which move together in parallel when the slide 8 is displaced. The position shown in full lines and designated as corresponds to the neutral position at which the two bimetallic strips 3 and are at the same temperature. Upon increasing displacement of the slide 8 in the arrowed direction due to heating of himetallic strip 5, when position I is reached the switch A corresponds to the switching interval for switch A and the angle between positions III and IV corresponds to the switching interval for switch B. The position IV for restoring the switch B after the said switch has changed to the operating position, however, cannot be achieved by the action of the bimetallic device C since, as mentioned, the position 0 corresponds to the neutral position thereof.

On the contrary, a restoring device G which can be operated from the outside of the apparatus is provided for this purpose. A restoring key 27 is displaceably mounted in a base 26 and can be pressed inwards from the outside in opposition to the leaf spring 28. The sloping end face of the key 27 then pushes the lever 20, which is in position 0, and thus the slide 8 towards the left, accompanied by bending of the bimetallic device, until position IV is reached and the switch B changes over to the rest position.

Near the control arrangement which has been described, the flame detector relay D with winding 21 and yoke 22 is mounted on the base plate 1. When a flame is present, the tumbler armature H composed of the two sheet metal elements 23 and 24 is attracted in opposition to the tensile force of the restoring spring 25. In doing so, it operates the normally closed contact of of relay D; the left-hand end of the part 23 is bent-over in such a manner that when the armature H is attracted it cooperates with the lever 14 which is in position I. This lever and with it the entire control arrangement is then locked in position I, Without'the heating of the bimetallic strip 5 necessarily being continued.

The connection diagram FIG. 4 shows schematically the parts which have already been described and the way in which they are connected together with the other components of the control and supervising apparatus. The circuit is connected to the A.C. supply by means of supply conductors 30 and 31. The flame detector arrangement comprises a photo-conductive resistor P which is exposed to the light of the burner flame. When light impinges, its resistance varies (signal p, FIG. 1), and this signal is amplified by the amplifier V whose output feeds the relay D. Thus, if a flame is established, relay D is excited and its contact d open.- The amplifier is fed by the transformer U. The amplifier is of a per se known type and preferably transistorized so that it is ready for operation instantly after the supply circuit is closed. The burner flame is ignited by the ignition transformer Z, and the burner motor M serves for feeding the oil-air mixture. Two glow lamps E (ready lamp) and F (fault lamp) are provided for indicating the working state of the apparatus. A further fault lamp F can be connected in parallel with lamp F and may be located at a point remote from the apparatus. Limiting resistors R are connected in series with the aforesaid glow lamps. In the case illustrated, a thermostat T is provided for controlling 4 the start and shut down of the plant (signal t, FIG. 1), but of course this control could be effected by a time switch or by means of a hand-operated switch as well.

The control and supervising apparatus operates in the following manner:

The apparatus is in the starting position when the switches A and B are in the position of rest shown in FIGS. 2 and 4, and therefore the levers 14 and 20 are in the position 0. In this case, the readly lamp E lights up, its circuit being completed from conductor 30 through the rest side of switch A and the motor M to conductor 31 (the lamp current is, of course, much too small to start the motor). The start of the oil burner is initiated when the thermostat T closes its contact. As a result of this, current is supplied to the amplifier V through the transformer U over the rest side of switch B and the aforesaid thermostat contact. At the same time, by way of the normally closed contact d of relay D, the igniting transformer Z and the heating coil 6 of the bimetallic device C are energized, and normally the ignition spark is established. But if any stray light falls on the photo-conductive resistor P--which would later impede the signalling of an extinction of the flamethe relay D is energized, its contact d opens, and ignition is prevented.

With the aforesaid initiation of ignition and the heating of the bimetallic device begins the so-called preignition period during which the strip 5 deviates in the direction indicated by the arrow, shifting the slide 8 and levers 14 and 20. In the case of a break in the heating circuit, e.g. a defect in the heating coil 6, this deviation does not take place, i.e. the burner does not come into operation. Thus, the pro-ignition period serves above all for the self-control of the apparatus and insures the full generaLion of the ignition spark before the supply of fuel begins.

After heating for about 20 seconds, position I is reached, in which the switch A moves to the operating position. This constitutes the end of the pre-ignition period and the beginning of the flame inception period. The burner motor M now receives current from conductor 30 through the rest side of switch B and the operating side of switch A (signal m, FIG. 1). Thus, the delivery of oil and air begins, the ignition and the heating of the bimetallic device still being continued. As a result, the flame is built up, the photo-conductive resistor P is illuminated and the relay D at the output of the amplifier is energised and opens its contact d, whereby ignition and heating of the bimetallic device are interrupted. If the flame extinguishes again, a new ignition process takes place immediately.

With the response of the flame detector relay D, on the one hand, as mentioned above, the contact d of the said relay opens and as a result the ignition andv the heating of the bimetallic device are discontinued. Furthermore, the attracted armature H engages behind and locks the lever 14 which is in position I, so that the entire control arrangement remains in this position, although the bimetallic strip 5 subsequently cools and tends to return to the position of rest. The state described corresponds to the normal working state of the burner.

If, however, for any reason, no flame is formed and therefore the relay D is not energized, the deviation of the bimetallic strip 5 is increased owing to the continued heating until, after a flame inception period of about 20 seconds, the position III is reached in which the switch B also changes over into the operating position. This fault position III is reached as well, although after a correspondingly longer time, if the flame burns only intermittently, i.e. for example for one second during each 20 seconds. Supervisory devices would be conceivable which return to the initial position at each impingement of light, but in such a case the fault position would never be reached despite the defective operation of the bumer.

In the operating or fault position of switch B, the circuits for the burner motor, the bimetallic strip heating system, the ignition system and the supply to the amplifier are interrupted, and on the other hand the fault lamp F, and also F if appropriate, has current supplied over the operating position of switch B, so that the fault is made visible externally (signal f, FIG. 1). With progressive cooling of the bimetallic strip 5, the slide 8 then returns to the position 0, the switch A again taking up the rest position when the position II is passed. The switch B, however, continues to remain in the fault (operating) position since the bimetallic device by itself brings the slide 8 only into the position and not into the position IV. The latter position, and thus the actual re-setting of the supervising apparatus, can only be achieved by deliberate actuation of the restoring key G from the outside after clearing the fault, upon which actuation the switch B rocks into the rest position and the fault lamps F and F goes out. It is to be mentioned here that accidental pressing of the key G in the normal working position remains ineffective, since in this case the key moves past the lever 20 which is in the position I.

As already mentioned, in the normal operating position the lever 14 is locked in position I merely by the attracted armature H, whilst the bimentallic strip 5 is not heated. If in such a case the flame detector indicates an extinction of the flame, the relay armature falling back releases the said lever and the bimetallic strip springs back into position 0, shifting the slide 8 and re-setting the switch A. This is followed automatically by a complete new ignition attempt.

If the thermostat calls for discontinuation of heat production, its opening contact interrupts the supply of the amplifier V, and relay D falls off, the burner becoming inoperative in the same way. It is brought back into operation again only upon closure of the thermostat contact.

What we claim is:

1. An apparatus for controlling and supervising an oil burner, said oil burner comprising, in combination with a source of electrical energy, flame igniting means connected with said source, a burner motor connected with said source and means connected with said source for indicating faulty state of burner; said apparatus comprising a first changeover snap action switch connected with said motor, a first rockable lever, a second change-over snap action switch connected with said source, a second rockable lever, a slide operatively connected with said switches and said levers, means connected with said source and said slide and adapted to move said slide after flame ignition from a neutral position to an operating position and thence to a fault indicating position, said slide during movement from said neutral position to said operating position swinging the first switch from a starting position to an operating position and moving the first lever from a neutral position to an operating position, said slide during movement from said operating position to said fault indicating position swinging the second switch from a starting position to a fault indicating position and moving the second lever to an operating position, said motor being actuated when the first switch is in its operating position, flame detector means operable when said motor is actuated, locking means connected with and actuated by said flame detector means to lock the first lever in its operating position, thereby locking the first switch in its operating position, said motor and said slide-moving means being disconnected from said source and said faulty-state indicating means being connected with said source when the second switch is in its operating position, and restoring means adapted to engage the second lever in a neutral position and to swing it to move said slide until the second switch is swung from the fault indicating position to the operating position, the angle between the two positions of the second lever at which the second switch is actuated being greater than the angle between the two positions of the first lever at which the first switch is actuated, said two positions of the second lever being located beyond said two positions of the first lever in relation to the movements of the first lever, said neutral position of the slide being located intermediate an actuating position of the first switch and an actuating position of the second switch.

2. An apparatus for controlling and supervising an oil burner, said oil burner comprising in combination with two supply conductors of a source of electrical energy, flame igniting means connected with one conductor, a relay contact connected with said flame igniting means, a thermostat connected with said relay contact, a burner motor connected with said one conductor and a fault indicating lamp connected with said one conductor; said apparatus comprising a first change-over snap action switch having a switching element and two switch contacts, said switching element engaging one switch contact in a starting position and engaging the other switch contact in an operating position, said switching element being connected with said motor, said one switch contact being connected with the other conductor, a first rockable lever adjacent said first switch, a second changeover snap action switch having a switching element and two switch contacts, the switching element of the second switch engaging one switch contact of the second switch in a starting position and engaging the other contact of the second switch in a fault indicating position, the switching element of the second switch being connected with the other conductor, said one contact of the second switch being connected with the other contact of the first switch, the other contact of the second switch being connected with said fault indicating lamp, a second rockable lever adjacent said second switch, a slide operatively connected with the switching elements of the two switches and said levers, a bimetallic device having a transmission element engaging said slide and including a bimetallic strip connected with said transmission element and a coil heating said bimetallic strip and connected with said one conductor and said relay contact, said bimetallic strip being adapted to move said slide from a neutral position to an operatin position and thence to a fault indicating position, said slide during movement from said neutral position to said operating position swinging the first switch from the starting position to the operating position and moving the first lever from a neutral position to an operating position, said slide during movement from said operating position to said fault indicating position swinging the second switch from the starting position to the fault indicating position and moving the second lever to the operating position, flame detector means operable when said motor is actuated, locking means connected with and actuated by said flame detector means to lock the first lever in its operating position, thereby locking the first switch in its operating position, and restoring means adapted to engage the second lever in a neutral position and to swing it to move said slide until the second switch is swung from the fault indicating position to the operating position.

3. An apparatus in accordance with claim 2, wherein said restoring means comprise a movable restoring key having a sloping end fact adapted to engage the second lever and to push it along with said slide until the second switch is swung from the fault indicating position to the operating position.

References Cited in the file of this patent UNITED STATES PATENTS 1,876,281 Eiseman Sept. 6, 1932 1,961,802 Taylor June 5, 1934 2,138,244 Raney Nov. 29, 1938 2,964,102 Cassell et al Dec. 13, 1960 

1. AN APPARATUS FOR CONTROLLING AND SUPERVISING AN OIL BURNER, SAID OIL BURNER COMPRISING, IN COMBINATION WITH A SOURCE OF ELECTRICAL ENERGY, FLAME IGNITING MEANS CONNECTED WITH SAID SOURCE, A BURNER MOTOR CONNECTED WITH SAID SOURCE AND MEANS CONNECTED WITH SAID SOURCE FOR INDICATING FAULTY STATE OF BURNER; SAID APPARATUS COMPRISING A FIRST CHANGEOVER SNAP ACTION SWITCH CONNECTED WITH SAID MOTOR, A FIRST ROCKABLE LEVER, A SECOND CHANGE-OVER SNAP ACTION SWITCH CONNECTED WITH SAID SOURCE, A SECOND ROCKABLE LEVER, A SLIDE OPERATIVELY CONNECTED WITH SAID SWITCHES AND SAID LEVERS, MEANS CONNECTED WITH SAID SOURCE AND SAID SLIDE AND ADAPTED TO MOVE SAID SLIDE AFTER FLAME IGNITION FROM A NEUTRAL POSITION TO AN OPERATING POSITION AND THENCE TO A FAULT INDICATING POSITION, SAID SLIDE DURING MOVEMENT FROM SAID NEUTRAL POSITION TO SAID OPERATING POSITION SWINGING THE FIRST SWITCH FROM A STARTING POSITION TO AN OPERATING POSITION AND MOVING THE FIRST LEVER FROM A NEUTRAL POSITION TO AN OPERATING POSITION, SAID SLIDE DURING MOVEMENT FROM SAID OPERATING POSITION TO SAID FAULT INDICATING POSITION SWINGING THE SECOND SWITCH FROM A STARTING POSITION TO A FAULT INDICATING POSITION AND MOVING THE SECOND LEVER TO AN OPERATING POSITION, SAID MOTOR BEING ACTUATED WHEN THE FIRST SWITCH IS IN ITS OPERATING POSITION, FLAME DETECTOR MEANS OPERABLE WHEN SAID MOTOR IS ACTUATED, LOCKING 